Bring the drop position into .NET and add the DOM hit test

app/MindWork AI Studio/Tools/Rust/DropPosition.cs

@@ -0,0 +1,13 @@
+namespace AIStudio.Tools.Rust;
+
+/// <summary>
+/// The cursor position of a drag and drop event.
+/// </summary>
+/// <remarks>
+/// The coordinates are viewport-relative CSS pixels, on every platform. The Rust runtime has already
+/// dealt with the platform differences -- device pixels on Windows, logical points on macOS and Linux --
+/// so these numbers can be handed to the browser for a hit test without any further conversion.
+/// </remarks>
+/// <param name="X">The distance from the left edge of the viewport, in CSS pixels.</param>
+/// <param name="Y">The distance from the top edge of the viewport, in CSS pixels.</param>
+public readonly record struct DropPosition(double X, double Y);